This invention relates generally to digital error correction and more particularly to digital error correction on selected orthogonal or semi-orthogonal codes generated in a linear feedback shift register (LFSR).
It is well known by those skilled in the art that in a synchronous data communication system synchronization information must be continuously or periodically sent from the transmitter to the receiver to initiate and maintain synchronization. Loss of synchronization can result in total loss of the transmitted information. Accordingly, it is imperative that a reliable means be found to increase the probablity of initiating and maintaining synchronization between a transmitter and one or more receivers.
A major problem in trying to synchronize a receiver to a transmitter is encountered when the synchronization information is corrupted by noise. Those skilled in the art will appreciate that a signal transmitted over a communication channel may become corrupted by noise due to atmospheric disturbances, physical disruptions in the channel or simply background random noise. Therefore, given that the synchronization information may be corrupted by noise, and thus received in error, some communication systems attempt to correct the received information to facilitate synchronization.
Prior art techniques have typically employed either parity bits interleaved between synchronization information bits or check word bits transmitted at the end of a synchronization bit sequence to attempt to correct errors at the receiver. However, transmitting either parity bits or check word bits (which are simply redundant synchronization information bits) reduces the synchronization information data rate because time is wasted sending the redundant information. Stated another way, the transmission of parity bits or check word bits requires additional bandwidth that may not be available in a crowded spectural environment.
Accordingly, a need exists to provide a reliable means of initiating and maintaining synchronization between a transmitter and one or more receivers that does not require the transmission of redundant information to enable synchronization information correction at the receivers.